This is just a general treatment of sealed lead acid batteries of the type used in the Vagabond system, but it should be useful in helping to get the best service from your batteries.
First, the primary rule to follow is to avoid draining your sealed lead acid batteries flat. They last longer, and retain higher capacity if they are not cycled way down, and if they are charged to capacity quickly thereafter.
Storing them flat (discharged) invites permanent capacity losing chemical changes, and exposes them to the possibility of mechanical damage at sub freezing temps from the formation of ice crystals that do not occur in a charged lead acid battery. Even if you can't help sucking your batteries dry during a shoot, never store them in a discharged state. That goes double when it is very cold.
The nature of lead acid chemistry is such that demanding high current flow in sub freezing temps will result in less apparent capacity, but things should return to normal when temps rise. If you are are shooting heavily on battery power alone in a sub freezing environment, you would be well served to have a charged spare battery set on hand.
Reasonably high temps are not so much a storage issue, as a charging/high current draw issue. You can cause permanent damage to a battery by cooking it while charging. Of course, that has much to do with the charging circuit as well. I'm betting that Paul designed the Vagabond to properly charge it's batteries, but even then, I would be cautious about charging for extended periods in 110 degree weather.
The last note I'd like to pass on is that sealed lead acid batteries do have a limited life, even when given TLC. I maintain about 2,000 batteries of that type alone at my day job, and have found that even in standby mode, with a reasonably smart low current charge maintenance circuit, they start to drop like flies after six years or so. Dry as a bone, and dead as a brick. Keep that lifespan in mind, as even if your mileage varies, a sealed battery will never outlast a good spouse. Batteries that see regular use other than standby tend to have somewhat less of a lifespan on average.
Those are my observations over a decade or so, and the results have been consistent. Still, sealed lead acid batteries offer awesome bang for the buck in terms of energy density, suitability over environmental extremes, reasonable size, and just plain cost economy.
If you beat up your batteries on a regular basis, buy a spare or two to share the load. If your stock battery compliment does everything you need it to do, make a mental note to consider buying a fresh spare battery pack after about 3-4 years of use. Don't buy ahead of time if you won't put it into service within a year or so. Buy sealed lead acid batteries when you need them, not too much before. Unlike lead acid auto batteries that are shipped without electrolyte installed, sealed lead acid batteries start their life clock when they leave the factory.
Enjoy the power!
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